3GPP Long Term Evolution, LTE, is the fourth-generation mobile communication technologies standard developed within the 3rd Generation Partnership Project, 3GPP, to improve the Universal Mobile Telecommunication System, UMTS, standard to cope with future requirements in terms of improved services such as higher data rates, improved efficiency, and lowered costs. The Universal Terrestrial Radio Access Network, UTRAN, is the radio access network of a UMTS and Evolved UTRAN, E-UTRAN, is the radio access network of an LTE system. In an UTRAN and an E-UTRAN, a User Equipment, UE, is wirelessly connected to a Radio Base Station, RBS, commonly referred to as a NodeB, NB, in UMTS, and as an evolved NodeB, eNodeB or eNB, in LTE. A base station is a general term for a radio network node capable of transmitting radio signals to a UE and receiving signals transmitted by a UE.
In-band Full Duplex, FD,—or full duplex for short—technology makes it possible that a wireless node transmits and receives communication signals using overlapping or even identical frequency resources for reception and transmission simultaneously. It is intuitively clear that FD communication may double the spectral efficiency, although this upper bound is typically not reachable in practice. However, FD communication has the potential to increase the spectral efficiency due to the progress in designing self-interference, SI, cancellation receivers that can reach up to 80-90 dB or even higher SI cancellation capabilities. This level of SI capability can be sufficient, especially in small cell networks, where the typical distance and large scale fading between the radio network node and wireless device is relatively small to increase the spectral efficiency of FD links as compared with Half Duplex, HD, links.
The transmission modes in FD communication systems can be categorized in terms of the involved nodes and their capabilities. Bidirectional Full Duplex, BFD, communication involves a pair of FD capable nodes that send and receive signals to one other on the same frequency channel at the same time. In contrast, in Three-Node FD, TNFD, communication a FD capable node communicates with two other (not necessarily FD capable) nodes such that the FD capable node transmits and receives signals to/from the non-FD capable nodes on the same frequency channel simultaneously.
Controlling the wireless device transmit power plays an important role in uplink, UL, Quality of Service, QoS, management, intercell interference, ICIC, mitigation and complying with regulatory constraints in terms of radio frequency, RF, spectrum emissions. In LTE, UL power control is supported by various parameters and measurements on reference signals that enable a UE to determine its transmit power levels on the physical resource blocks, PRB, that the UE is scheduled on.
For LTE, the maximum allowed UL transmit power depends on the power class that the UE belongs to. For example, for UEs of Class-3, the maximum transmit power is 23 dBm+/−2 dB for all allowed frequency bands. In addition, the maximum power reduction, MPR, parameter (specified in 3GPP TS 36.101 V13.3.0 (2016-03)) requires the UE to further reduce its maximum transmit power by 1 or 2 dB depending on the modulation scheme and the bandwidth configuration used by the UE for the UL transmission.
In addition to the MPR parameter, the network can signal the Additional MPR, A-MPR, to the UE. The A-MPR specifies an additional power reduction depending on the frequency band, channel bandwidth, the number of physical resource blocks allocated and the modulation depth. The MPR and A-MPR parameters enable the UE to comply with requirements related to spurious emissions, Adjacent Channel Leakage power Ratio, ACLR, additional spurious emission and Out-Of-Band, OOB, emission (in parts specified in 3GPP TS 36.101 V13.3.0 (2016-03)) that are part of the UE RF testing aspects according to 3GPP TS 36.521-1 V13.1.0 (2016-03).
However, when the wireless access point (e.g. a base station) and the served user equipment are capable of BFD or TNFD communications, the maximum power reduction, MPR, and the additional maximum power reduction, A-MPR, parameters do not help the wireless network to comply with the regulatory rules concerning the RF aspects of UE transmissions. Hence, there is a need for improved methods of controlling power in BFD or TNFD communications.